A major revolution in video display technology includes flat screens based on either liquid crystal display (LCD) or plasma display panel (PDP) technology that are rapidly replacing the cathode ray tube (CRT) technology that served as the primary display device for more than a half a century. A significant consequence of the new video display technologies is that pictures may now be displayed at higher picture-rates with progressive scanning on a flat screen. The new video display technologies may also facilitate a faster transition from standard definition television (SDTV) to high-definition television (HDTV). However, legacy video compression systems still use formats with lower picture-rates and may be unable to optimally display legacy video on modern display screens.
There may be restrictions on channel capacity that may affect the display of low picture-rate pictures. For example, considering a 30 Hz video sequence that may be broadcast over a mobile network, the terminals, for example, mobile phones may receive an encoded video sequence from a server. However, due to bandwidth limitations, only a low bit-rate video sequence may be communicated. As a result, the encoder may remove two out of every three pictures to be transmitted, resulting in a sequence with a picture rate of about 10 Hz, for example. The terminal may be capable of displaying video at 30 Hz but since it receives a 10 Hz video, it may have to perform some form of picture-rate conversion.
The available channel capacity may be different in diverse video services. The legacy systems may be different in different regions of the world, for example, NTSC, SECAM or PAL. The picture rate requirements may differ depending on applications and users. Picture-rate conversion may be required in a plurality of applications in order to adapt to a wide variety of display systems. The video picture rate up-conversion may be divided into one or more categories, for example, conversion from interlace to progressive scan or 50/60 Hz interlace to 50/60 Hz progressive, picture rate doubling, for example, 50 Hz to 100 Hz or 60 Hz to 120 Hz, non-integer scan rate conversion, for example, 50 Hz to 60 Hz.
An artifact known as “motion judder” may occur when the picture rate of a video sequence is excessively low. Motion judder may occur when the temporal sampling rate is too low to describe motion in a scene. The objects in input pictures may be shifted on either side of a required output picture. A temporal digital filter interpolation method may be used to determine pixel intensity values. The signals describing motion of each of the objects within a scene may be referred to as motion vectors. Each pixel or region with the same movement may be allocated a motion vector. The motion estimation system may determine these motion vectors and failing to find a correct motion vector and/or misusing the motion vector in a picture rate converter may lead to noticeable artifacts. When large camera movements occur, regions of a picture close to the borders may have significantly less reliable motion vectors than those closer to the middle and special processing may be required at the picture boundaries.
Further limitations and disadvantages of conventional and traditional approaches will become apparent to one of skill in the art, through comparison of such systems with some aspects of the present invention as set forth in the remainder of the present application with reference to the drawings.